This is a randomized prospective study to compare the efficacy of fully suppressive vs partially suppressive doses of 1-thyroxine in shrinking abnormal thyroid tissue, and to evaluate changes in bone density which may occur in patients taking suppressive doses of 1-thyroxine, and to determine if any documented adverse effects of 1-thyroxine on peripheral organs can be minimized by using partially suppressive, rather than fully suppressive doses of 1-thyroxine. Previous data by MGH investigators have suggested that ""suppressive"" doses of thyroxine may be asociated with osteoporosis. A highly sensitive (3rd generation) assay allows discrimination between partially and fully suppressive thyroxine doses. There are insufficient data to report any conclusions at the present time. Final data analysis will occur after all patients have been enrolled and prospectively followed. The investigators plan to continue to accrue data for all enrolled patients.